1. Field of the Invention
The present invention relates a fluid turbine, and more particularly, to a fluid turbine which is used in a fluid coupling or retarder.
2. Description of the Related Art
A fluid retarder is typically used as an auxiliary brake for large vehicles such as trucks and buses. This type of retarder is mounted on the output side of a transmission and connected to the drive shaft of the vehicle. A rotor and a stator are enclosed in an operation chamber and disposed adjacent to each other. The rotor is fixed to the drive shaft and both rotate together in unison when the vehicle is in motion and the transmission is engaged. The stator is fixed to the housing and does not rotate. Both the rotor and the stator include an annular shell, and a plurality of blades are arranged radially inside the respective shells. An oil sump containing oil is disposed adjacent to the housing. When compressed air is fed to the oil sump, the oil contained in the oil sump is forced into the housing. When the rotor is rotating, the oil is displaced radially outward by centrifugal force and flows in the rotational direction of the rotor. The oil is then forced against the blades of the stator, which forces the oil to flow in a direction opposite to the rotational direction of the rotor. The oil is then directed back to the rotor. Because the oil is flowing in a direction opposite to the rotational direction of the rotor, the rotation of the rotor and the drive shaft are slowed, thereby slowing the vehicle.
Because the rotor in a fluid retarder is subjected to a high amount of torque, the rotor is typically cast from one or more metals. However, casting the rotor can result in high manufacturing costs. It is also possible to manufacture the shell and the blades from sheet metal and weld the two components together in order to reduce the cost. However unlike the rotor blades in a torque converter, the rotor blades in a retarder are not supported by a core ring. This makes it is difficult to maintain the high mechanical strength necessary for the rotor blades to withstand the high amount of torque generated within the retarder.